[4] Cochran and co-authors Jason Hardy and Henry Harpending suggest that the high average IQ of Ashkenazi Jews may be attributed to natural selection for intelligence during the Middle Ages and a low rate of genetic inflow.
[8] In 2000, Cochran and evolutionary biologist Paul W. Ewald co-authored a paper in which they proposed that most human diseases were the result of pathogenic infections (viruses, bacteria, parasites).
Cochran and Ewald point to stomach ulcers, which were once thought to be caused by a variety of environmental factors such as smoking, diet and drugs, but were later attributed to bacteria.
[11][10] In 1999, journalist Caleb Crain published an article in the gay magazine Out in which he spoke with Cochran and several sexual orientation researchers about the hypothesis.
[15] The dominant hypothesis in the scientific literature is that male homosexuality may be a result of organisational effects of sex hormones on the brain during fetal development.